Final answer:
In isometric muscle contractions, muscle tension increases while the muscle length remains the same due to the load exceeding the tension the muscle can produce, resulting in no movement of the load.
Step-by-step explanation:
During isometric contractions, there is an increase in muscle tension but the muscle length remains unchanged. This is because the load being lifted exceeds the maximum tension that the muscle can generate.
Consequently, there is no movement of the load and the muscle does not change length. In contrast to isotonic contractions, where the muscle length changes such as during a biceps curl, isometric contractions are static and often involved in activities such as maintaining posture or stabilizing joints.